kunit: mock: print the mock method name when the return value is missing

1. not check the type of retval, the return from the mock method.
2. abort the test and output the mock method name in the error message, if the return value is empty.

Google-Bug-Id: 110154346
Signed-off-by: Lin Xinan <linxinan@google.com>
Change-Id: Ife1ac37153284e2583c0e5c13ada6288cd5c2cfe
1 file changed